Strain-based fatigue analysis of wheelchairs on a double roller fatigue machine

Results are presented from an experimental program that recorded the outputs of strain gages mounted on two wheelchair frames (one manual, one power) as the wheelchairs were run on a double roller fatigue machine. Rectangular strain gage rosettes were attached to the frames near the cross tube center pin and on the side frame behind a front caster. Thirty data sets were recorded from each rosette on each wheelchair frame. The fatigue test machine and test protocol were in substantial conformance with the recently published ANSI/RESNA Standard for wheelchair fatigue testing. Two analyses have been performed on the recorded strain data. The von Mises stress histories were computed from the strain data and show that peak stresses are frequently twice the mean value. Also, estimates of the number of fatigue machine cycles to failure have been made using a strain-based fatigue analysis. These data will provide wheelchair designers with useful data to incorporate into their design process.